Variable velocity constant exhaust system



Oct. 6, 1964 B. c. EGE 3,151,954

VARIABLE VELOCITY CCNSTANT EXHAUST SYSTEM Filed Nov. 28, 1960 WEB WEB Am 5mm SUPPLY FAN Fig. l

WEB

Z0 LL11 I 1 I WITH MOTORS 1 i0 7Louvialz n mvzas Fig. 2

EXHHUST FAN Fig. 3 Z? EXHAUST FAN SUPPLY FAN INVENTOR.

BENDT C. EGE

"aw 402w? United States Patent 3 151354 VARIABLE VELQCITY CONSSTANT EXHAUST SYSaTiEM Bendt C. Ege, Wantagh, N.Y., assignor to Midland-Ross Corporation, Cleveland, Ghio, a corporation of Ghio Filed Nov. 23, 19:35), Ser. No. 72,083 5 Claims. (Cl. 34-155) This invention relates to a method of and apparatus for drying and, more particularly, to that type of drier wherein a web, length or ribbon of material to be dried is continuously translated in and through a drying chamber or enclosure while drying medium such as heated air is passed over, through or across the web. The web may be the material or article to be dried, or it may be a support or conveyor on which the material is distributed for translation through the drying chamber.

In drying materials, which have been treated with explosive solvents, the requirements are severe for an acceptable drier, that is, one operating efficiently while conforming to safety requirements. It is necessary in such situations that the drying air be kept within a narrow temperature range while at the same time the velocity of the drying air over the material being dried must vary widely to accommodate difierent web speeds, solvent volumes per unit mass of material being dried, and the rate of drying itself. Furthermore, when the web itself is the article being dried, the rate of circulation of drying medium must be very low when the web is stopped for insertion of a new web or for its attachment to the trailing end of a previous web. At the other extreme, the velocity of drying medium must be a maximum when the web is being run at its optimum or maximum speed.

While, theoretically, it would be easy to vary the speed of the blowers or fans inducing the flow of drying medium over the load in direct proportion to the speed at which material is being conveyed through the drier, the problem is actually complicated, first because of the severe requirements for a variable speed drive of this nature or for varying the speed of the driving motors, and secondly, because safety requirements preclude the use of variable speed drives for exhaust fans where explosive solvents are involved.

It is, therefore, the principal object of the invention to provide a drying process and apparatus wherein the speed of the drying medium in, over or through the load may be varied over a wide range of velocities, without varying the speed of the blowers, fans or other impellers.

Mother object is to provide a drying process and apparatus of the moving web or conveyor type wherein a constant volume of circulated air or other gaseous drying medium is variably diverted between two paths between inlet and exhaust, one over and/ or through the load and a second around or by-passed about the load.

A still further object is to provide a drier of the moving web type wherein the volume of drying air may be varied as in the preceding object and also wherein that portion of the medium being directed over the load may be variabiy divided between blasts directed to the load upon opposite sides thereof.

Yet another object is to provide a drier which wherein reciprocally varying amounts of a constant volume of rying medium passed through the drying chamber per unit time, may be directed to drying and by-pass, respectively.

A still further object is to provide an apparatus and method for drying wherein material to be dried is passed through a drying chamber at speeds or mass/time rates depending upon the amount of solvent or other liquid, per unit mass of dry material, production rates, etc. a constant mass/ time rate of heated drying medium is introduced into, and exhausted from the drying chamber, and

Patented @ot. 6, I964 a portion of the drying medium so introduced is directed into drying contact with the material, which portion is varied in accordance with the instantaneous speed or mass/time rate of passage of materials into and through the drying chamber.

Other objects and advantages of the invention will be apparent to those skilled in the art, after a study of the following detafled description in connection with the accompanying drawing.

In the drawing:

FIGURE 1 is a view showing in plan, and partly in section, one embodiment of the invention;

FIGURE 2 is an elevation, partly in section on line 2-2 of FIGURE 1; and

FIGURE 3 is an elevation corresponding generally to FIGURE 2, showing a modified form.

Referring in detail to the drawing, 1 identifies a drier housing of generally rectangular form in horizontal and vertical sections, through which a web W is translated at known velocity and which may be supported on rollers, not shown, or in other known ways for passage through the housing.

Within the housing a first header 2 is positioned over the web with openings, not shown, extending the entire width of the web and so disposed as to direct drying medium downwardly upon the web. Similarly a second header 3 is disposed transversely of and beneath the web and is provided with slots or other apertures, not shown, disposed to direct drying medium upwardly against the lower surface of the web. In both headers 2 and 3, the apertures therein are arranged to divide the air substantially uniformly over the width or transverse dimension of the traveling web.

The upper and lower headers 2 and 3, are supp ied from a fan 5 shown as a centrifugal type drawing air from a heater 6 with intake at 7, axially through inlet 8. The outlet of the fan is connected with a conduit 9. As shown upon FIG. 2, this conduit is divided to form a first pair of upper passages 1i? and 11, and a second pair of lower passages 12 and 13. Each passage has therein louvers or dampers identified at 14, i5, 16 and 17, respectively. Each set of louvers is adjustable to vary the rate of flow through its respective passage. It is contemplated also that the adjusting means for the sets of louvers may be interconnected. For example, louvers 14 and 2.5 may be interconnected in a manner not shown, to open one set while simultaneously closing the other set, so that the volume of air through passage 11 and header 2, for example, may be increased simultaneously with decrease of volume through passage 16.

Passage 1% enters housing 1 but, as shown at FIG. 2, drying air passing through it is by-passed therethrough and does not flow over or across the load. Passages 11 and 12 are connected with headers 2 and 3, respectively, so that all air supplied thereto is directed into, through or over the load. Passage 13 is connected with the housing 1 but, like passage 10, air supplied thereto is by-passed and does not pass in contact with the load.

Air is exhausted from housing 1 by a fan 15? through an exhaust duct 18 and directed to ambient air through an outlet 20. It is contemplated that this outlet ma ,in certm'n installations, be connected with intake 7 so that a portion of the drying air at least, may be recirculated.

In operation with web W traveling through housing or chamber 1 at known speed, or conveying material thereon through the chamber at known mass/time rate, and with the supply and exhaust fans passing heated drying air, or other medium, through the chamber at constant flow rate, the amount of drying air directed into drying contact with the load or material traversing the chamber, may be varied over a wide range, from minimum when louvers 15 and 16 are closed and louvers 14 and 17 open, to a 3 J maximum when and 16 are fully open and 14 and 17 closed.

Furthermore, by inversely varying the amounts of drying medium passed by louvers 15 and 16, the proportion of air directed to the two surfaces of the web may be correspondingly varied. The adjustments of the louvers may be effected manually or automatically, based upon the flow rate of drying air, temperature thereof, solvent content per unit mass of dry material being dried, speed of conveyance of materials, etc.

FIGURE 3 shows a modification wherein drying air is directed onto one side only of the traveling web. In this figure, 1a indicates the drying housing, chamber or enclosure, in cross section, and through which a web, ribbon or belt 4a is translated in a direction normal to the plane of the figure. A supply blower or fan 24} is connected to direct drying medium through a conduit 21 through one side Wall of the chamber, while a second or exhaust fan 22 draws air from the chamber, through a conduit 23 from the opposite side wall.

At its entrance to the chamber In conduit 21 is provided with a horizontally-disposed partition 24 forming the top wall of a header or duct 2.5 having a closed end 26 and an open bottom or, alternatively, a bottom provided with slots or apertures, not shown, forming the only outlet for drying medium therein, to direct the same downwardly upon the Web 40. As will be noted, header is positioned in spaced relation with and below the top wall 29 of the chamber, to provide a bypass or passageway 13%) through which drying air may pass directly from inlet to exhaust, without contact with web 4a, or material thereon.

A first set of louvers 27 are adjustable to vary the flow of air to header 25, while a second set of louvers 28 are adjustable to vary the flow through by-pass 3%. Thus, in a manner obvious from FIGURE 3, the fiow of drying medium to and over the load or web 4:: may be varied over a wide range, while the delivery of air to and from the drying chamber remains constant, that is, the speeds of supply fan 20 and exhaust fan 22 may remain constant.

In practice, by a coordination of dampers, or louvers 14 to 17, FIGURES 1 and 2, or 27, 28, FIGURE 3, it is possible to vary the velocity of drying medium over the load, over a wide range of, for example, 3000 to 7000 cubic feet per minute, without, however, any change in speeds of the blowers.

Having now fully disclosed the invention, what I claim and desire to secure by Letters Patent is:

1. A traveling web drier comprising, a drying chamber through which a web is continuously longitudinally translated, a first header in said chamber positioned across said web at one side thereof to direct drying air thereagainst, a second header in said chamber positioned across said web at the other side thereof to direct drying air thereagainst, there being first and second by-passes in said chamber adjacent each of said headers, respectively, an exhaust fan connected with said chamber to exhaust drying air therefrom, a supply fan, a conduit conducting drying air from said supply fan to said chamber, means dividing the flow through said conduit into first, second, third and fourth discrete passageways connecting with said first by-pass, said first header, said second header and said second by-pass, respectively, and two sets of louvers, each in a respective one of said passageways leading to said headers, each said set of louvers being individually adjustable to vary the flowof drying air therethrough between said supply fan and said exhaust fan.

2. A traveling web drier comprising, a drying chamber through which a web is continuously longitudinally translated in a horizontal path, a first header in said chamber positioned over and across the web path to direct drying air downwardly onto a web, a second header in said chamber positioned beneath and across the web path to direct drying air upwardly against a web, there being first and second by-passes in said chamber above and below said first and second headers, respectively, an exhaust fan connected with said chamber to exhaust drying air therefrom, a supply fan, a conduit conducting drying air from said supply fan to said chamber, means dividing the flow through said conduit into first, second, third and fourth discrete passageways connecting with said first and second headers and said first and second by-passes, respectively, and four sets'of louvers, each in a respective one of said passageways, each said set of louvers being individually adjustable to vary the flow of drying air therethrough between said supply fan and said exhaust fan.

3. A dryer comprising a closed housing, means to translate a Web of material through said housing in a straight planar pass, first and second headers insaid housing, each extending transversely across the web at and adjacent a respective side thereof, each said header being constructed and arranged to deliver drying medium onto a respective side of said web, uniformly distributed completely thereacross, means forming a by-pass to conduct drying air directly through said housing, without contacting said web, first, second and third discrete damper means in said first and second headers and said by-pass, respectively, each operable to vary the flow rate therethrough, a supply blower, a conduit connecting the delivery of said blower to said headers, and blower means connected with said housing to exhaust therefrom air flowing through said headers and said by-pass.

4. In a dryer, vertically-spaced top and bottom walls and side and end walls, all interconnected to form a closed drying chamber into and out of which a traveling web of material is translated, through said end walls in a planar horizontal pass, a header mounted in said chamber to extend horizontally and transversely across said pass closely adjacent the same and adapted to discharge a drying medium vertically and uniformly distributed against said pass, said header being spaced from the contiguous wall of said chamber to define a by-pass for conducting drying medium directly and transversely through said chamber without contact with said pass, a first conduit connected with said header and said by-pass through an opening in one side wall of said chamber to supply drying medium thereto, a second conduit connected with an opening in the other side wall of said chamber to exhaust drying medium from said chamber, power-driven blower means connected to force drying medium to, and exhaust the same from said first and second conduits, respectively, and at a constant uniform rate of flow, first louver means in said header and operable to vary the rate of flow of drying medium therethrough into contact with said pass, and second louver means in said by-pass and operable to vary the rate of flow of drying medium through said by-pass, said first and second louver means being adjustable to inversely vary the rates of flow of drying medium through said header and by-pass, to maintain constant the rate of flow through said chamber while varying from substantially zero to maximum, the rate of flow of drying medium through said header, and contacting said pass.

5. In a dryer vertically-spaced top and bottom walls and side and end walls, all interconnected to form a closed drying housing into and out of which a traveling web of material is translated through said end walls in a planar horizontal pass, a first header mounted in said housing to extend horizontally and transversely across said pass closely adjacent and above the same, a second header mounted in said housing to extend horizontally and transversely across said pass closely adjacent and below the same, said headers having discharge openings to direct drying medium vertically and uniformly distributed against and completely across said pass, said first header being spaced vertically below said top wall to define a first bypass, said second header being spaced vertically above said bottom wall to define a second by-pass, said bypasses conducting drying medium through said housing without contact with said pass of Web material, a first conduit connected with all said headers and by-passes to supply drying medium thereto through an opening in one said side wall, a second conduit connected with an opening in the other said side Wall to exhaust drying medium from said housing, power-driven blower means connected with said first conduit to supply drying medium thereto at constant rate of flow, a first pair of louvers in said first and second conduits, respectively, and adjustable to vary the rates of flow of drying medium therethrough, a second pair of louvers in said first and second by-passes, respectively, and adjustable to vary the rates of flow of drying medium therethrough, said first and second pairs of louvers being operable to inversely vary the rates of flow of drying medium through said headers and said bypasses, to vary from essentially zero to maximum, the

rate of flow of drying medium into contact with said pass, while maintaining constant the rate of flow of drying medium through said housing.

References Cited in the file of this patent UNITED STATES PATENTS 1,995,675 Furbush Mar. 26, 1935 2,268,987 Hess Jan. 6, 1942 2,571,815 Benoit Oct. 16, 1951 2,696,055 Murphey Dec. 7, 1954 2,775,046 Kabelitz Dec. 25, 1956 2,857,682 Olden Oct. 28, 1958 2,955,342 Litzler Oct. 11, 1960 3,012,335 Allander Dec. 12, 1961 

1. A TRAVELING WEB DRIER COMPRISING, A DRYING CHAMBER THROUGH WHICH A WEB IS CONTINUOUSLY LONGITUDINALLY TRANSLATED, A FIRST HEADER IN SAID CHAMBER POSITIONED ACROSS SAID WEB AT ONE SIDE THEREOF TO DIRECT DRYING AIR THEREAGAINST, THERE BEING FIRST AND SECOND BY-PASSES IN SAID CHAMBER ADJACENT EACH OF SAID HEADERS, RESPECTIVELY, AN EXHAUST FAN CONNECTED WITH SAID CHAMBER TO EXHAUST DRYING AIR THEREFROM, A SUPPLY FAN, A CONDUIT CONDUCTING DRYING AIR FROM SAID SUPPLY FAN TO SAID CHAMBER, MEANS DIVIDING THE FLOW THROUGH SAID CONDUIT INTO FIRST, SECOND, THIRD AND FOURTH DISCRETE PASSAGEWAYS CONNECTING WITH SAID FIRST BY-PASS, SAID FIRST HEADER, SAID SECOND HEADER AND SAID SECOND BY-PASS, RESPECTIVELY, AND TWO SETS OF LOUVERS, EACH IN A RESPECTIVE ONE OF SAID PASSAGEWAYS LEADNG TO SAID HEADERS, EACH SAID SET OF LOUVERS BEING INDIVIDUALLY ADJUSTABLE TO VARY THE FLOW OF DRYING AIR THERETHROUGH BETWEEN SAID SUPPLY FAN AND SAID EXHAUST FAN. 